Valve for pneumatic percussive tools



n. w. WILSON. VALVE FOR PNEUMATIC PERCUSSIVE TOOLS.

APPLICATION FILED JUNE 3' 1920.

1,361,431 Patented Dec. 7, 1920.

UNITED STATES PATENT OFFICE.

REGINALD WELLESLEY WILSON, OF NEWCASTLE-UPON-TYNE, ENGLAND, ASSIGNOB TO SIR W. G. ARMSTRONG, WHITVJORTI-I AND COMPANY, LIMITED, OF NEWCASTLE- UPON-TYNE, ENGLAND.

VALVE r03 PNEUMATIC PERCUSSIVE TOOLS.

Specification of Letters Patent.

Patented Dec. 7, 1920.

Application filed June 8, 1920. Serial No. 387,503.

To all whom it may concern Be it known that I, REGINALD WELLESLEY WILSON, a subject of the King of Great .Valves for Pneumatic Percussive Tools, of

which the following is a specification.

This invention relates to pneumatic percusive tools such as hammers, riveters and calkers, and its object is to provide a simpler and more efficient tool than those hitherto used.

According to this invention the automatic supply of compressed air to the two ends of the cylinder alternately is controlled by an automatic valve which is in the form of a ring having at the rear a flange the front of which may be coned or flat. The valve is capable of a small to and fro movement in a valve box at the rear end of the cylinder. Ports or passages formed in the valve box allow compressed air to act upon the front and rear surfaces of the flange. When the valve is moved forward air passes longitudinally through itto drive the piston forward, but when the valve is moved back air can pass around the front of the flange and so to the front of the cylinder to move the piston back. The supply of air to the 1nterior of the handle is controlled by two throttle valves in such a way that the first movement of the operating lever or trigger opens one valve only to admit a hmited supply of air so that a light blow 1s dealtby the piston, while further movement of the lever or trigger opens both valves to admit a full supply of air so that a heavier blow is dealt.

The invention is illustrated by the accompanying drawing, which is a section of a pneumatic hammer.

1 is the cylinder or barrel in the frontof which can' be secured a tool 2 and in Wl'llCll reciprocates a piston 8. The rear end of the cylinder screws into a handle 4 1n which is pivoted a lever5 which can be actuated by the user to control the admlssion of air under pressureto a space 6 in the handle.

Between the rear of the cylinder and a shoulder 7 in the handle is fitted a valve box consisting of a part 8 and a back ring or cover 9. While the part 8 may for convenience of manufacture be a separate part as shown in the drawing, it is obvious that it may be integral with the cylinder 1. In the valve box works an automatic valve 10 which is in the shape of a ring having a flange the front surface of which is coned so that it can seat against a corresponding cone in the valve box. The valve is capable of a small reciprocating movement between the cover 9 and the part 8. In the rear face of the cover is cut an annular groove 11 which is always in communication with the space 6 in the handle. A port (or ports) 12 cut through the cover allows air to pass from the groove 11 to the rear face of the valve 10 and a port (or ports) 13 allows air to pass from the groove. 11 to a passagelt opening into the cone in the part 8. In the part 8 is formed an annular chamber 15 from which a port (or ports) 16 leads to the front of the valve 10. A passage 17 bored through-the wall of the cylinder 1 leads from the chamber '15 to a groove 18 near the front of the cylinder. 19 is an exhaust port cut through the wall of the cylinder.

The entry of compressed air from the nozzle 20, to which it is supplied by a flexible pipe, to the space 6 in the handlevis controlled by two valves 21 and 22. The valve 21 consists of a tube closed at each end and having its lower end a sliding fit through valve 22, the upper surface of which is coned so that it can seat itself against a corresponding cone 23 in the interior of the handle. When the tool is not in use the valves are kept in the position shown in the drawing by the pressure of the air and if necessary also by a spring 24 which acts upon the valve 22 and a spring 25 lying between the top of the valve 22 and a collar 26 on the top of valve 21. Between the top of valve 21 and the trigger 5 is a plunger 27 When it is desired to use the tool the operator presses lever 5 and thus depresses valve 21 which moves down through valve 22 so that air can pass through a port 28 into the interior of valve 21 and out through a port 29 into the space 6. A further movement of the lever causes a shoulder 30 in valve 21 to come against the top of the valve 22 which is therefore moved from its seat so that an increased supply of air can pass around valve 22 into the space 6 and the piston 8 is thereby caused to deal heavier blows to the tool 2, while when valve 22 is on its seat air can only pass to the cylinder through the interior of valve 21. A stop 81 pivoted above the lever 5 determines the amount of movement of the latter. In the position shown the lever cannot be moved and therefore no air can pass to the cylinder. When, however, the stop is turned counterclockwise so that its surface 32 comes opposite the lever the latter can be turned to open valve 21, but no matter what the ressure on the lever it cannot be moved any farther. .When however the stop is turned still farther to bring the surface 33 opposite the lever the latter can then be moved to open the valve 22. When either valve 21 or valves 21 and 22 are opened the action is as follows Assuming the piston 3 to be at the forward end of its stroke, the rear part of the cylinder is open to the atmosphere through port I 19. Valve 10 will move rearward owing to the pressure of the air passing through port 13 and passage 14 and acting on the coned portion of the flange of the valve. The valve will therefore close port 12 but air can now pass from passage 14: in front of valve 10,through port 16, chamber 15, passage 17 and groove 1 8.to the front of piston 3 which will therefore be driven back. When the front of piston 3 uncovers port 19 the pressure in front of the piston will be released as will that in front of valve 10-. The rearward movement of the piston will compress the air trapped in the rear of the cylinder and the pressure of this air on the part of the rear of the flange which is nearest the axis of the valve together with the pressure of the air entering throughport 12 and acting upon the rear face of the valve will move the valve forward so that it closes passage 14 and port 16. Air will then flow from groove 11 through port 12 and through the middle of valve 10 and will drive the piston forward. It will be seen that the interior diameter of the valve is less than the interior diameter of the rear of the cover 9 1 but only to a small extent so that the air trapped in the rear of the cylinder will have to be highly compressed before it has effect upon the rear face of the valve and moves 7 the latter forward on to its seating. Thus the rear end of the piston reaches a point very near the front face of the cover before the valve is moved on to its seating and so it is possible for the piston to have a long stroke and to impart a heavy blow to the tool 2.

As soon was the piston in its forward movement covers port 19 air is trapped in the front of the cylinder and this air is compressed during the last part of the forward stroke of the piston so that a pressure is created in the chamber 15 As soon as the rear of the plston has unthe cylinder and therefore on the rear face of the valve falls so that the pressure in the chamber 15 together with that in passage 14L, moves the valve rearward again and the cycle of operations is repeated.

What I claim is 1. In a pneumatic tool, the combination of a cylinder having in its Wall a longitudinal passage from the rear to the front and an exhaust port near the middle point in its length, a piston within the cylinder, a handle secured to the rear of the cylinder and having in it an air space, means for admitting compressed air to this space, a valve box at the rear of the cylinder, a valve in the form of a ring having a flange at its rear and capable of a small to and fro movement within'the valve box, a port adapted to allow air to pass from the space in the handle to the rear of the flange of the valve, a passage adapted to allow air to pass from the air space to the front of the flange of the valve and a port adapted to allow air to pass from the front of the flange of the valve to the longitudinal passage.

2. In a pneumatic tool, the combination of a cylinder having in its wall a longitudinal passage from the rear to the front and an of the valve, a port adapted to allow air to pass from the space in the handle to the' rear of the flange of the valve, a passage adapted to allow air to pass from the air space to the front of the flange of the valve and a port adapted to allow air to pass from the front of the flange of the valve to the longitudinal passage.

3. In a pneumatic tool, the combination of a cylinder having in its wall a longitudinal passage from the rear to the front and an exhaust port near the middle point of its length, a piston within the cylinder, a handle secured to the rear of the cylinder and having in it an air space, means for admit-' ting compressed air to this space, a valve box at the rear of the cylinder, av valve in the form of a ring having a flange at its rear and capable of a small to and fro move ment within the valve box, a port adapted to allow air to pass from the space in the handle to the rear of the flange of thevalve, a passage adapted to allow air topass from the air space to the front of the flange of the valve, an air chamber in the valve box communicating with the rear of the longitudinal passage and a port adapted to allow air to pass from the front of the flange of the valve to the air chamber.

4. In a pneumatic tool, the combination of a cylinder having in its wall a longitudinal passage from the rear to the front, and an exhaust port near the middle point of its length, a piston within the cylinder, a handle secured to the rear of the cylinder and having in it an air space, means for admitting compressed air to this space, a valve box at the rear of the cylinder, a valve in the form of a ring having a flange at its rear and capable of a small to and fro move- Inent within the valve box, the interior diameter of the rear of the valve box being larger than the interior diameter of the rear of the valve, a port adapted to allow air to pass from the space in the handle to the rear of the flange of the valve, a passage adapted to allow air to pass from the air space to the front of the flange of the valve, an air chamber in the valve box communicating with the rear of the longitudinal passage and a port adapted to allow air to pass from the front of the flange of the valve to the air chamber.

In testimony that I claim the foregoing as my invention I have signed my name this 18th day of May 1920.

REGINALD WELLESLEY WILSON. 

